Allyl-containing epoxy resin composition comprising a copolymer of an ethylenically unsaturated anhydride and a vinyl compound

ABSTRACT

The invention relates to a resin composition comprising epoxy resin, a cross linking agent for the epoxy resin in the form of a carboxylic anhydride, and at least one allyl network forming compound. According to the invention, the anhydride-functional compound is a copolymer of an ethylenically unsaturated anhydride and a vinyl compound. Notably suitable are styrene-maleic anhydride copolymers known as SMA Type 1. Surprisingly, it was found that the presence of at least 2 wt.% of triallyl cyanurate (TAC) results in an increase in Tg, such that even with simple difunctional epoxy compounds resins can be obtained which have a glass transition temperature of 130° C. and higher. It was further found that the processing as prepreg of epoxy resins cross-linked using anhydride-vinyl copolymers will be greatly enhanced by the presence of at least 10 % of allyl.

The invention pertains to a resin composition comprising epoxy resin, across-linking agent (curing agent) for the epoxy resin in the form of acarboxylic anhydride, and at least one allyl network forming compound.

BACKGROUND OF THE INVENTION

Such resin compositions are known from EP 413 386. This document relatesto IPNs (Interpenetrating Polymeric Networks) having very favorableproperties, in particular for use in the electronics industry. This isthe case when the cross-linking agent used for the epoxy resin is apolyhydric phenol. In actual practice, the embodiment using anhydridecross-linking agents proves unsatisfactory. Notably, the Tg obtained istoo low, and the electrical properties and the prepreg stability alsoleave room for improvement.

In addition, it is desired that the use of inexpensive difunctionalepoxy resins should give thermal properties which are of the samestandard as can be obtained using the multifunctional epoxy resinspreferably employed in EP 413 386. Resins based on multifunctional epoxycompounds have been described in WO 85/03515 and WO 86/02085.

Other publications describing allyl-epoxy resin compositions employinganhydrides as cross-linking agent for the epoxy resin are U.S. Pat. No.2,707,177, DE 35 21 506, GB 994 484, and EP 417 837. This last patentspecification teaches the use of ethylenically unsaturated anhydrides,such as maleic anhydride, where the anhydride not only cross-links theepoxy resin but also takes part in the forming of the allyl network.

In JP 04-44287 and in JP 04-015211 a resin composition for flexibleprinted circuits is described. The resin composition comprises aphtalate based compound with at least two allyl groups per molecule, acopolymer made from ethylene and an α,β-unsaturated dicarboxylic acidand/or its anhydride, and a copolymer made from ethylene and anethylenic unsaturated monomer containing an epoxy group. The compositiondescribed here is a specific grafted IPN. As the composition describedcomprises thermoplasts rather than conventional epoxy resins, thiscomposition is not suitable for use in prepregs.

The use of adducts of ethylenically unsaturated anhydrides and aromaticacids as cross-linking agent for epoxy resin is described in BE 627 887.This patent publication also discloses a proposal to use copolymers ofmaleic anhydride and styrene (SMA) as cross-linking agent for epoxyresin. A drawback to such epoxy resin compositions is that they cannotbe used to make so-called prepregs.

Prepregs are widely employed in the manufacture of laminates for theelectronics industry, in particular for printed-wire boards. Suchmanufacture involves impregnating a supporting or reinforcing fabricwith a resin, followed by partial curing of said resin. Such impregnatedfabric is commonly referred to as prepreg. Manufacturing a printed-wireboard involves laminating one or more layers of prepreg with, say, oneor more layers of copper.

Processing prepregs into boards usually involves their being cut down tosize and laminated. Both these process steps make stringent demands onthe resin with which the fabric is impregnated. For instance, thepartially cured resin has to have sufficient sturdiness and a highviscosity, yet it must be sufficiently sticky and liquid to give goodadhesion when laminated, and hence good interlaminar strength. The resinmay not be too highly reactive, since this will render the requiredpartial curing impossible.

In this connection resin compositions where the epoxy resin iscross-linked with an anhydride-containing copolymer have the drawback ofbeing too brittle to be processed as prepregs. For instance, it provesimpossible to cut up such prepregs without a portion of the resinblowing about in the form of a large quantity of dry dust. This issometimes called a "mushroom effect", after mushroom spores blowingabout.

One the one hand, the invention has for its object to enhance thethermal and electrical properties of resin compositions based on allylcompounds and epoxy-resin cross-linked with anhydride. One the other,the invention envisages providing resin compositions based ondifunctional epoxy resin which have thermal and electrical propertiescomparable to those of resin compositions based on multifunctional epoxycompounds. Furthermore, the invention aims to provide resin compositionswhere the problem of brittleness, which occurs when SMA is used as epoxycross-linking agent, can be prevented.

SUMMARY OF THE INVENTION

To this end, the invention consists of a resin composition of the typementioned in the opening paragraph where the carboxylic anhydride is acopolymer of an ethylenically unsaturated anhydride and a vinylcompound. In such a copolymer the ethylenically unsaturated portion ofthe anhydride is incorporated into the backbone. The carboxylicanhydride groups remain intact, and they are available as functionalgroups for cross-linking the epoxy resin.

DETAILED DESCRIPTION OF THE INVENTION

Examples of suitable ethylenically unsaturated anhydrides include maleicanhydride, fumaric anhydride, itaconic anhydride, citraconic anhydride.Examples of suitable vinyl compounds include ethylene, propylene,butylene, isobutylene, styrene, α-methyl styrene. Copolymers of maleicanhydride have been described, int. al., in Encyclopedia of PolymerScience and Engineering Vol. 9 (1987), page 225 ff. Within the frameworkof the invention the term "copolymer" likewise refers to polymers intowhich mixtures of unsaturated anhydrides and/or mixtures of vinylmonomers have been incorporated (e.g., terpolymers of maleic anhydride,ethylene, and styrene).

Preference is given to copolymers of styrene and maleic anhydride (SMA),which are commercially available in two types. Type 2 comprises mostlyhigh-molecular weight terpolymers (MW generally higher than 100,000,e.g., 1,000,000). These are in fact thermoplasts, which are unsuitablefor use in the manufacture of prepregs. Moreover, because of their lowanhydride content (5-15%) they are not particularly suitable for use asa cross-linking agent for epoxy resin either. The type 1 SMA copolymers,on the other hand, which have a molecular weight in the range of about1500 to about 50,000 and an anhydride content of more than 15%, arepre-eminently suited to be used. Preference is also given to SMAcopolymers having a molecular weight in the range of 1500 to 10,000.Examples of such copolymers include the commercially available SMA 1000,SMA 2000, and SMA 3000. These copolymers have a styrene:maleic anhydrideweight ratio of 1:1, 2:1, and 3:1, respectively, and a molecular weightranging from about 1400 to about 2000.

The amount of copolymer employed can be such as will give ananhydride:epoxy equivalency ratio in the range of 30 to 110%. When using20 wt.% or more of allyl compound, the ratio selected preferably isbetween 75 and 100%. When using less than 10 wt.% of allyl compound, thepreferred anhydride:epoxy ratio ranges from 40 to 60 equivalent %.

In addition to the copolymeric cross-linking agent there may be used apolyhydric phenol cross-linking agent. Examples of polyfunctionalaromatic hydroxyl compounds include dihydroxy compounds of the formulaeshown in U.S. Pat. No. 5,210,157. Furthermore, Novolac resins such asphenol/-formaldehyde, cresol/formaldehyde orphenol/p-hydroxybenzaldehyde can function as polyfunctional aromatichydroxyl cross-linking agents. The anhydride/vinyl copolymer can also becombined with other types of epoxy cross-linking agents, such asamine-containing cross-linking agents (e.g., dicyanodiamide) andlow-molecular weight anhydrides (e.g., methyl tetrahydrophthalicanhydride, methyl hexahydrophthalic anhydride, nadic methyl anhydride,hexahydrophthalic anhydride, benzophenone tetracarboxylic anhydride,tetrahydrophthalic anhydride). The selection of an additionalcross-linking agent applies in particular when extra flame retardancy isdesired. Preferred in this connection is tetrabromo bisphenol-A. Theadditional cross-linking agent will generally be used in such an amountas to give a copolymer:phenol equivalency ratio of 90:10 to 10:90,preferably of 90:10 to 40:60.

The term "epoxy resin" in this context refers to a curable compositionof oxirane ring-containing compounds as described in C.A. May, EpoxyResins, 2nd Edition, (New York & Basle: Marcel Dekker Inc.), 1988.

Examples of epoxy resins include phenol types such as those based on thediglycidyl ether of bisphenol-A, on polyglycidyl ethers ofphenol-formaldehyde Novolac or cresol-formaldehyde Novolac, on thetriglycidyl ether of tris(p-hydroxyphenol)methane, or on thetetraglycidyl ether of tetraphenyl ethane; amine types such as thosebased on tetraglycidyl methylene dianiline or on the triglycidyl etherof p-aminoglycol; cycloaliphatic types such as those based on3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate. The term"epoxy resin" also stands for reaction products of compounds containingan excess of epoxy (e.g., of the aforementioned types) and aromaticdihydroxy compounds. These dihydroxy compounds may be halogensubstituted.

Preference is given to epoxy resins of the phenol type, especially onaccount of their low price. This holds particularly for epoxy resinsbased on difunctional epoxy compounds such as bisphenol-A bisepoxide andother diglycidyl ethers (such as the diglycidyl ether of bisphenol-F,sulphon diphenol, tetrabromobisphenol-A). As a rule, the glasstransition temperature of such bisepoxides does not exceed about 120° C.A significant advantage of the resins according to the present inventionlies in the fact that the combination of anhydride-vinyl copolymers ascross-linking agent and the presence of at least 2 wt.% of triallylcyanurate (TAC) results in a much higher Tg (130°-190° C.) beingobtained, while resin proccessability continues to be excellent.

It is possible to introduce fire retardancy not just into thecross-linking agent but also into the resin itself, usually by means ofincorporating halogenated compounds. Thus tetrabromobisphenol-A inparticular is a well-known component of epoxy resins suitable for use inthe present invention.

It should be noted that epoxy resins are generally represented by asingle, unequivocal structural formula. The skilled person will knowthat this should be taken to include deviating products resulting fromside reactions occurring during epoxy resin preparation. As these sideproducts constitute a normal component of cured epoxy resins, theylikewise constitute a normal component of the resins according to theinvention.

Cross-linking of the epoxy resin generally proceeds with the aid of anaccelerator. As suitable accelerators may be mentioned imidazoles, moreparticularly alkyl substituted imidazoles such as 2-methyl imidazole and2-ethyl-4-methyl imidazole, and tertiary amines, e.g., benzyl dimethylamine.

The amount used of such an accelerator is dependent on the type of epoxyresin, the type of cross-linking agent, and the type of accelerator.Employing a too large amount of accelerator will lead to a too highlyreactive resin system. Such a system is not serviceable for makingprepregs. The skilled person can easily determine within which range aresin system will be just sufficiently little reactive to allow readyprocessing into prepregs. In general, such a processing range will bebetween 0.01 and 5 wt.% of accelerator, calculated on the overall weightof epoxy resin and cross-linking agent. In many cases this will be the0.01-0.075 wt.% range. The gel time for its part is dependent on thetype and amount of accelerator, the type and amount of solvent, and thetype of prepreg to be manufactured. In the specific case of 2-methylimidazole (2MI) being used as accelerator and SMA copolymers serving ascross-linking agent, it is preferred not to use more than about 0.025wt.% of 2MI. By way of general guideline it can be said that it isadvisable not to have a system gel time of less than 120 seconds.

Examples of suitable allyl monomers formed into an allyl polymer networkvia cross-linking under the influence of radicals include triallylcyanurate (TAC), triallyl isocyanurate (TAIC); aromatic polyallyl esterssuch as diallyl phthalate, diallyl isophthalate, triallyl trimellitate,tetraallyl pyromellitate, diallyl tetrabromophthalate; aliphaticpolyallyl esters such as diallyl adipate, diallyl maleate, diallylfumarate, and polyallyl carbonates such as diethylene glycol diallylcarbonate.

Alternatively, mixtures of allyl monomers and allyl prepolymers may beemployed to prepare resins according to the invention.

The polyallyl compounds in the resin can be partially replaced byaromatic difunctional methacrylates, such as described in U.S. Pat. No.5,210,157. Preferably, use is made of2,2-di(4-methacryloxy-ethoxyphenyl)propane (BMEPP).

The desired resin properties determine the amount of allyl to beincorporated into the resin and the type of allyl compound. According tothe invention, for instance, it has surprisingly been found that the Tgof epoxy resins cross-linked with the aid of copolymers of maleicanhydride and vinyl compounds (such as SMA) can be increasedsubstantially by the use of at least 2% of triallyl cyanurate (TAC).This is even the case when apart from the TAC (preferably 2-20%) thereare no other allyl compounds. The Tg effect found is such, however, asto increase the Tg of every epoxy resin. Most surprisingly of all, it isnow possible, as indicated above, to obtain resins having glasstransition temperatures of 130° C. and higher even with simpledifunctional epoxy compounds.

A further surprising result according to the invention consists in thatthe incorporation into the resin of at least 5%, and preferably morethan 10%, of any allyl compound will give resins where the use ofanhydride copolymer cross-linking agents does not produce a mushroomeffect. Preferably, 10-60 wt.% of allyl is used. Optimum results, i.e.,those which produce both a higher Tg and good prepreg proccessability,are attained with at least 10 wt.% of TAC present in the resin.

It should be noted that even when the amount of allyl is low (say, 2-5%of TAC), the resin according to the invention differs substantially fromthe epoxy resin in its unmodified form. In this connection it has to beconsidered surprising that a major epoxy resin property, i.e., the Tg,is increased so strongly at the much lower TAC contents mentioned. At ahigher allyl content the resin according to the invention will differfrom the epoxy resin to a greater extent. The allyl compounds are alwaysused in conjunction with a radical initiator, and so will form a polymernetwork not chemically bonded to the epoxy network. As a rule, it tendsto be very evident in this connection that at allyl contents of morethan 10 wt.% there is question of an IPN (interpenetrating polymernetwork): in the (at least partially) cured form the resin according tothe invention in that case will comprise an intimate physicalinterlinking, on a molecular scale, of the two chemically differingnetworks. This results in a single Tg and the enhancement of several keyproperties, such as resistance to chemicals, dielectrical properties,and prepreg flexibility.

In general, the initiator is used in a ratio of 0.1-5 wt.% vis-a-vis theallyl compound. Suitable initiators include peroxides, such as t-butylperoxybenzoate, t-butyl peroxy-3,5,5-trimethyl hexanoate, and benzoylperoxide. Alternatively, thermal polymerisation can be carried outwithout an initiator.

As a rule, an organic solvent is employed when preparing resinsaccording to the invention. One advantage of the use of TAC as IPNcomponent is that is can also act as a solvent. If an additional solventis used, it must be one in which the epoxy resin, cross-linking agent,and polyallyl compound are soluble, while the solvent itself should besufficiently volatile to evaporate before or during the partial curingof the IPN, or else before its final curing.

As suitable solvents may be mentioned dimethyl formamide; glycol etherssuch as ethylene glycol mono-ethyl ether or propylene glycol mono-ethylether and their esters such as ethylene glycol mono-ethyl ether acetate;ketones such as methyl isobutyl ketone, methyl ethyl ketone, acetone,and methyl isopropyl ketone; aromatic hydrocarbons such as toluene andxylene. Alternatively, mixtures of solvents can be employed. Thepreferred solvents are ketones, notably acetone and methyl ethyl ketoneor mixtures of these with ethers, notably propylene glycol mono-ethylether.

The invention further pertains to laminates for use in the electronicsindustry incorporating resins of the aforementioned type.

Laminates for use in the electronics industry (particularly forprinted-wire boards) are generally produced by impregnating a supportingor reinforcing material (usually based on glass fibres, either as awoven fabric or in the form of a cross-ply laminate of unidirectionallyoriented parallel filaments) with a resin, followed by the resin beingcured wholly or in part. The latter process is the most common one, anda fabric impregnated with a partially cured resin is usually referred toas a "prepreg." To make a printed-wire board from a prepreg fabric oneor more layers of the prepreg are laminated with, say, one or morelayers of copper.

The resin used generally is an epoxy resin. The present practicalstandard is the FR4-laminate, which is based on a brominated epoxy resinprepared from a diglycidyl ether of bisphenol-A andtetrabromo-bisphenol-A, dicyanodiamide as curing agent, an organicsolvent, an accelerator, and a catalyst. The drawback to such an epoxyresin is its low Tg (110°-135° C.), while in addition the dicyanodiamidehas a tendency to crystallize in the resin and the prepreg madetherefrom.

The resins according to the invention are highly suitable forimpregnating, e.g., woven fabric and cloth of a variety of materialssuch as glass, quartz, carbon, aramid, and boron fibres, moreparticularly to make laminates for printed-wire boards. This applicationpreferably calls for the resin to be employed in combination with aglass fabric.

It was found that even when it is based on simple difunctional epoxycompounds, the combination of resin components according to theinvention will give excellent properties for application in theelectronics industry. The Tg effect has been mentioned earlier: ascompared with the corresponding standard epoxy resins (cured withdicyanodiamide) TAC-containing resins according to the invention have aTg of about 30°-50° C. higher. Furthermore, it was found that resinsaccording to the invention exhibit a much better resistance to short,intense temperature increases than do standard FR4 epoxy resin and IPNsaccording to EP 413 386. This is demonstrated by the solder shock test,which is known to the skilled man. In this test a material istransferred abruptly from room temperature to solder having atemperature of 288° C. The material (in this case a laminate made of aresin according to the invention) floats in the solder, and so will besubject to a temperature gradient (and hence a tension gradient). Thematerial should be capable of withstanding these conditions for at least30 seconds without bubble formation or delamination occurring. Thelonger the material can stand the test, the more serviceable it will befor use in printed-wire boards. The resins according to the inventionare capable of standing the solder shock test for 10 minutes, whichrepresents a substantial improvement over both the aforementioned knownIPNs, which bear it for about 3 minutes, and FR4 epoxy resin (about 4minutes). Furthermore, the resins according to the invention exhibit asignificant reduction of dielectric loss. Measured at 1 MHz (inaccordance with IPC TM-650, 2.5.5.1), the resins according to theinvention give a value of 10-11×10⁻³, as compared with 20-25×10⁻³ forFR4 epoxy and 15-20×10⁻³ for IPNs according to EP 413 386.

Also, the resins according to the invention can be employed wherever useis made of conventional epoxy resins: as a glue, coating, molding resin,embedding resin, encapsulating resin, sheet molding compound, bulkmolding compound.

In addition to being used as composites for printed-wire boards, theIPN-resins according to the invention can be employed to make compositesfor, int. al., the construction, aviation, and automobile industries.The manufacture of appropriate structural composites may proceed in aknown manner, e.g., by impregnating reinforcing material with molten ordissolved resin, or via resin transfer molding, filament winding,pultrusion, or RIM (reaction injection molding).

The resins according to the invention may contain the usual additivessuch as dyes or pigments, thixotropic agents, fluidity control agents,and stabilizers.

EXAMPLES

The invention will be further illustrated with reference to thefollowing unlimitative examples.

Example 1

(Comparison example)

An epoxy resin composition was prepared as formulated below: 45.5 g ofEpikote 1143B80 (FR-4 resin, ex Shell, epoxy equivalent weight 500, 21wt.% of bromine, 80% solution in methyl ethyl ketone) were combined with26.6 g of SMA3000 (ex Elf Atochem, MW average 2870). This quantity ofsolid SMA3000 had earlier been dissolved in 26.6 g of methyl ethylketone (MEK). Next, 158 mg of a 10%-solution of 2-methyl imidazole (in2-methoxy,1-propanol) were added (0.025 %, calculated on the solid resincomponents, i.e., solid FR-4 and SMA combined). The resin now contained0.131 equivalents of epoxy groups and 0.118 equivalents of anhydridegroups. The stoichiometry percentage (simply, equivalent percentage),i.e., the ratio of the number of equivalents of anhydride groups dividedby the number of equivalents of epoxy groups multiplied by 100, was90,3%.

This resin solution was poured into aluminum molds. Enough resin wasused to give a thickness after curing of 0.5 to 1 mm. The samples wereplaced in a forced-circulation air oven. The temperature of the oven wasset to 80° C. This temperature was maintained for about 1 hour, raisedin about 30 minutes to 120° C., and maintained for 30 minutes beforebeing raised again, this time to 180° C. in about 45 minutes. It waskept at 180° C. for 1 hour. On conclusion of this cycle the samples werecooled down slowly to room temperature, released from the molds, andsubjected to a thermal treatment at 200° C. for 2 hours.

Example 2

A mixture of the following resin components was prepared: 45.5 g ofEpikote 1143B80, 26.6 g of SMA3000 (dissolved in an even amount of MEK),and 10.0 g of TAC-prepolymer solution (70% in MEK). The resin contained0.072 equivalents of epoxy groups and 0.065 equivalents of anhydridegroups. The equivalent percentage equalled that of Example 1: 90.3%. Interms of percentages by weight, the composition of the formulation wasas follows: 52.0 wt.% of FR-4, 38.0 wt.% of SMA3000, and 10.0 wt.% ofTAC. The TAC-prepolymer solution had the following characteristics:Mw=143000, Mn=7100, dispersion of 20.1, conversion from the monomer tothe oligomer of 43%, solids content of 70%, and a Brookfield viscosityof 60 Mpa.s.

To the solution were added successively: 158 mg of a 2-methyl imidazolesolution (10 g of 2-methyl imidazole dissolved in 90 g of2-methoxy,1-propanol) and 70 mg of tert.-butyl peroxybenzoate. Curingtook place as described in Example 1.

Example 3

In a manner analogous to that described in Examples 1 and 2 a resin wasformulated and cured. This formulation contained only 3 wt.% of TAC. Theremainder of the composition, in percent by weight and calculated onsolids, was as follows: 41.0% of SMA3000 and 56.0% FR-4 resin. Thefollowing amounts were weighed in: 49.0 g of Epikote 1143B80, 28.7 g ofSMA3000 (dissolved in an even amount of MEK), 3.0 g of TAC-prepolymersolution, 170 mg of 2MI-solution (10% in 1-methoxy,2-propanol), i.e.,0.025% calculated on FR-4 and SMA combined, 21 mg of t.-butylperoxybenzoate, i.e., 1% vis-a-vis TAC. The formulation contained 0.078equivalents of epoxy and 0.070 equivalents of anhydride, giving anequivalent percentage of 89.7%.

Example 4

The same formulation except with 5 wt.% of TAC had the followingcomposition: 48.0 g of Epikote 1143B80 (54.8 wt.%), 28.1 g of SMA3000(dissolved in 28.0 g of MEK) (40.2 wt.%), 5.0 g of TAC-prepolymersolution (5.0 wt.%). For 0.025% of 2MI (relative to the solid epoxycomponents, FR-4 and SMA): 166 mg of a 10% solution. One percent oft-butyl peroxybenzoate in this case was 35 mg. The equivalent percentagewas 89.9%.

Example 5

An example containing 20 wt.% of TAC, analogous to the formulationsdiscussed above. The following quantities were employed:

40.4 g of Epikote 1143B80 (46.2 wt.%);

23.7 g of SMA3000 (dissolved in an even amount of MEK) (33.8 wt.%);

20.0 g of TAC-prepolymer solution;

140 mg of 2-methyl imidazole solution (10%);

0.025 % of 140 mg of t.-butyl peroxybenzoate, 1% vis-a-vis TAC solids;

The equivalent percentage was 90.3%.

The properties of the samples obtained as disclosed in Examples 1through 5 are compiled in Table

                  TABLE 1                                                         ______________________________________                                         Tg-measurements on the samples described in Examples 1 through 5!            # SMA3000                                                                     # equivalent percentage 90%                                                   # 0.025% of 2-methyl imidazole                                                example  1                                                                    no.      (comp.ex)  3       4      2     5                                    ______________________________________                                        composition:                                                                  % FR-4 resin                                                                           57.7       56.0    54.8   52.0  46.2                                 % SMA3000                                                                              42.3       41.0    40.2   38.0  33.8                                 % TAC    0          3.0     5.0    10.0  20.0                                 Tg (°C.)                                                                        100        110     135    185   165                                  TMA-method                                                                    ______________________________________                                    

Example 6

The resin of the composition indicated in Example 2 was used to makeprepregs and laminates, the amounts of accelerator and t-butylperoxybenzoate being changed, however, to 0.035% of 2-methyl imidazolevis-a-vis epoxy and SMA-solids and 3% of t-butyl peroxybenzoatevis-a-vis TAC-solids, respectively.

The composition of this resin solution was as follows:

# 1500 g of Epikote 1143B80

# 330 g of TAC-prepolymer (70% in MEK)

# 1758 g of SMA3000 solution (50% in MEK)

# 500 g of MEK

# 50 g of 2-methoxy,1-propanol

# 7.58 g of 2-methyl imidazole solution (0.758 g of solid 2-methylimidazole supplemented with 2-methoxy,1-propanol to 7.58 g)

# 6.9 g of t-butyl peroxybenzoate

The Brookfield viscosity was 100 mPa.s.

Standard E-glass, style 7628 with finish Z6032, was impregnated withthis resin using a laboratory treater. This process involved glassfabric of a width of about 50 cm being passed continuously through avessel containing resin solution. The fabric saturated with resin wasthen placed in a drying tunnel, where the solvent evaporated in thefirst section and the temperature moved through a gradient from 50° to170° C. In the second treater section, with the temperature at 170° C.,the resin, which was now solvent-free, was partially polymerized. Thispolymerisation stage is usually referred to as the B-stage, the materialis called a prepreg. The viscosity of the resin and the set speed of thetreater resulted in a prepreg having the following characteristics:resin yield 44-48 wt.% and resin flow 19-24%. These values weredetermined in accordance with test procedures drawn up by the IPC(Institute for Interconnecting and Packaging Electronic Circuits).

In a hydraulic press equipped with a vacuum chamber the thus preparedprepregs were compressed to form a laminate. To this end 8 prepregs of50×50 cm were deposited on copper foil (1 ounce, electrodeposited type).Copper foil was also placed on top of the package, and the whole wasthen transferred to said press. The specific pressure during thecompression process was 15 ato. The press was heated at a rate of 5°C./min to 170° C., which temperature was maintained for 1 hour, afterwhich there was cooling at the same rate to 50° C., followed by thepress being opened. The laminate was subjected to a 2-hour thermalaftertreatment at 200° C. The thickness of the laminate ranged from 1.4to 1.6 mm.

The following properties were measured on the laminate: Tg (°C.) DMA:205° C. TMA: 170° C. DSC: 175° C.

Pressure Cooker Test

Water absorption (%) Test passed?

after 2 hr: 0.25 yes

after 4 hr: 0.35 yes

after 7 hr: 0.45 yes

Percentage of water absorption: 0.1%

Absorption of dichloromethane: 0.9%

Absorption of N-methyl pyrrolidone: 0.05%

Copper peel strength:

as received: 13 N/cm

after solder float: 13 N/cm

delamination: after > 10 minutes of solder float

Dielectric properties

(measured on a laminate having a thickness of 1.44 mm, with previousdrying of the sample)

    ______________________________________                                        frequency (MHz)                                                                              dielectric constant                                                                       loss factor                                        ______________________________________                                        0.1            4.4         0.0084                                             0.1            4.4         0.0089                                             1              4.3         0.0119                                             2              4.4         0.0109                                             10             4.2         0.0120                                             20             4.2         0.0119                                             50             4.2         0.0177                                             ______________________________________                                    

Examples 7 through 11

In the same manner as described in Examples 1 through 6 a series ofsamples having an equivalent percentage of 50 instead of 90 wasprepared. The composition and the Tg-values are compiled in Table

                  TABLE 2                                                         ______________________________________                                         Tg-measurements on the samples described in Examples 7 through 11!           # SMA3000                                                                     # equivalent percentage 50%                                                   # 0.010% of 2-methyl imidazole                                                example                                                                       no.      7          8       9      10    11                                   ______________________________________                                        composition:                                                                  % FR-4 resin                                                                           71.1       69.0    67.5   64.0  56.9                                 % SMA3000                                                                              28.9       28.0    27.5   26.0  23.1                                 % TAC    0          3.0     5.0    10.0  20.0                                 Tg (°C.)                                                                        104        116     125    142   152                                  TMA-method                                                                    ______________________________________                                    

Examples 12 through 14

These examples relate to laminates prepared in a manner analogous to theone disclosed in Example 6, except that this time use was made ofSMA1000 in the following equivalent percentages: 50, 70, and 110%. Theproperties of these laminates are compiled in Table

                  TABLE 3                                                         ______________________________________                                         properties of the laminates described in Examples 12 through 14!             example no.   12        13        14                                          ______________________________________                                        composition:                                                                  % FR-4 resin  75.0      70.3      62.6                                        % SMA1000     15.0      19.7      27.4                                        % TAC         10.0      10.0      10.0                                        equivalent-%  50        70        90                                          Tg (°C.)                                                               TMA           120-125   125-135   165-170                                     DSC           120-125   130-135   150-155                                     Pressure Cooker Test                                                          Water absorption                                                              after 2 hours:                                                                              0.34.sub.1                                                                              0.35.sub.1                                                                              0,46.sub.2                                  after 4 hours:                                                                              0.47.sub.1                                                                              0.49.sub.1                                                                              0,51.sub.2                                  after 7 hours:                                                                              0.60.sub.1                                                                              0.61.sub.2                                                                              0,60.sub.2                                  % water absorpt.:                                                                           .01       0.1       0.1                                         % CH.sub.2 Cl.sub.2 absorpt.:                                                               0.4       0.6       0.6                                         % NMP adsorpt.:                                                                             0.05      0.1       0.1                                         Copper peel strength                                                          as received:  :                                                                             15 N/cm   15 N/cm   17 N/cm                                     aft. solder float:                                                                          15 N/cm   15 N/cm   16 N/cm                                     delamination after                                                                          >10 min   >10 min   >5 min                                      solder float:                                                                 ______________________________________                                         .sub.1 Test passed                                                            .sub.2 Test not passed                                                   

Example 15

In Example 15 the laminate concerned is an epoxy cresol Novolac (codeECN1280) cured with a combination of SMA3000 and tetrabromobisphenol-A(abbreviation: TBBPA). The equivalent percentage of the twocross-linking groups combined is 90%. The composition and properties areas follows:

Composition:

ECN 1289: 45.0%

SMA 3000: 9.4%

TBBPA: 35.5%

TAC: 10.0%

The following properties were measured on the laminate:

Tg (°C.)

TMA: 185° C.

DSC: 185° C.

Pressure Cooker Test

Water absorption Test passed?

after 2 hours: 0.34 yes

after 4 hours: 0.38 yes

after 7 hours: 0.46 yes

Percentage of water absorption: 0.1%

Absorption of dichloromethane: 0.2%

Absorption of N-methyl pyrrolidone: 0.1%

Copper peel strength:

as received: 17 N/cm

after solder float 17 N/cm

delamination: after 7-8 minutes of solder float

We claim:
 1. A resin composition comprisingan epoxy resin, across-linking agent for the epoxy resin in the form of a carboxylicanhydride which is a copolymer of an ethylenically unsaturated anhydrideand a vinyl compound, a radical initiator, and triallyl cyanurate (TAC).2. The resin composition of claim 1 wherein the TAC is present in anamount of at least 2 wt.%.
 3. The resin composition of claim 1 whereinthe TAC is present in an amount of at least 10 wt.%.
 4. The resincomposition of claim 1 wherein the radical initiator is present in anamount of between 0.01 and 5 wt.%.
 5. The resin composition of claim 4wherein the TAC is present in an amount of at least 2 wt.%.
 6. The resincomposition of claim 1 wherein the cross-linking agent for the epoxyresin is a copolymer of styrene and maleic anhydride having a molecularweight of about 1400 to about 50,000 and an anhydride content of 15 to60 wt.%.
 7. The resin composition of claim 6 wherein the molecularweight is about 1400 to about 2000 and a styrene:maleic anhydride weightratio of 1:1, 2:1 or 3:1.
 8. The resin composition of claim 1 whereinthe copolymer is used such as to give an equivalency ratio of anhydrideto epoxy in the range of 30 to 110%.
 9. The resin composition of claim 1wherein a quantity of bromine atoms such as will give fire retardancy isincorporated into the epoxy resin.